The IEEE 1394 bus system is already known; it is a serial bus system which is self-configuring and is currently being expanded for operation as a vehicle communications network. Power saving modes have already been described in IEEE 1394a, where a device connected to such a serial bus system has four different activity states ranging from full activity to a complete shutdown. If a device is switched off completely, it must nevertheless have a basic functionality at the level of the bit transmission layer (physical layer) to be able to analyze the wake-up command in particular.